Tales of the Quantum: Understanding Physics’ Most Fundamental Theory

Book Preface

From Dr. Suess to the Hardy Boys to Tom Sawyer, the tales told in books were my most dependable boyhood buddies. I first encountered physics many years later, following a degree in music and a stint in the Army. As a student of physics at Kansas State University in Manhattan, I was delighted to find much of what I learned in textbooks and lectures to be fascinating, often strange, and always mind- expanding, stories. But now they were true stories, about a natural world that increasingly intrigued me. An account of the forces acting on an airplane, an elegant proof that Earth follows an elliptical path around the sun, or an account of the famous experiment demonstrating that light is a wave— all were fascinating adventures of the mind. Fifty- five years later, my love affair with nature persists.

This book tells tales of our quantum universe, in words accessible to everyone, without mathematics or unnecessary technicalities. My protagonist is the quantum, arguably the central actor on the cosmic stage. Although most popular books about quantum physics follow the subject’s history, Tales of the Quantum follows the phenomena: wave– particle duality, fundamental randomness, being in two places at once, and quantum jumps, to name a few. It presents history and people only to the extent that they illuminate the phenomena. Nevertheless, I hope Tales of the Quantum has a storylike quality that will be meaningful to both nonscientists and scientists. It’s written for all who would like to better fathom, before they depart this mortal coil, what makes the universe tick. Tales of the Quantum has a central message: quantum physics is fine and healthy just as it is. From the 1920s through today, the radical nature of the theory has prompted many, including Albert Einstein, to find fault with one or the other fundamental quantum precept and to try to fix it. But quantum physics doesn’t need fixing. The theory may be strange, but it’s not a mystery. We’ll discover that all its supposed paradoxes are resolvable and can be explained consistently in ordinary English without invoking algebra, technicalities, or supernatural powers.

The book’s most original feature is a suggested solution of the measurement problem, aka Schrödinger’s cat. Chapter 10 argues that the solution arises from a suggestion first made in 1968 and rediscovered by many physicists, including me, since that time. Working from this suggestion, my own research has shown that Schrödinger’s famous cat is not the outrageous “quantum superposition” of a dead cat and an alive cat that it at first appears to be, but is instead an entirely non-paradoxical “superposition of correlations” as I’ll explain in Chapter 10. In my view, measurement remains the only significant quantum foundational issue still in dispute. Regarded by some as unresolved, by others as resolved, and by still others as a mere pseudo- problem that needs no resolution, the problem splits the experts and is compounded by its title. By calling it the measurement problem, we suggest that quantum foundations have something to do with the human beings who make scientific measurements, leading some to conclude that quantum physics reinstates human minds at the center of physics for the first time since Copernicus. It’s even been seriously suggested that human consciousness is required for normal physical reality to emerge from the quantum world. The work of Wojciech Zurek and many others, although not entirely solving the measurement problem, has clarified that measurements are indeed crucial to understanding how quantum physics leads to the world of our experience. But these so- called “measurements” have nothing necessarily to do with humans; they are conducted constantly, all over the universe, by the environment. Human consciousness has no essential role in the foundations of quantum physics. Another distinctive facet is this book’s take on the famous issue of wave– particle duality. Is the universe made of waves in spatially extended “fields,” or of tiny particles, or both? As the title of my 2013 American Journal of Physics article states, “there are no particles, there are only fields.” The universe is made
entirely of fields, such as Earth’s gravitational field and the magnetic fields you’ve probably experienced when playing with magnets. With the notable exception of Richard Feynman, most quantum field theorists— physicists who integrate quantum physics with Einstein’s theory of relativity— have taken this viewpoint, but somehow it hasn’t filtered through to the broader ranks of physicists, other scientists, and the public.

Tales of the Quantum contains no mathematics beyond a few numbers. Mathematical physicist Paul Dirac stated, “Mathematics is only a tool and one should learn to hold the physical ideas in one’s mind without reference to the mathematical form.”1 But some physicists are convinced that any accurate presentation of quantum physics must be mathematical and thus can’t be understood by nonscientists, and that any popularly understandable presentation must be inaccurate. I heartily disagree! A plethora of good physics books, written in nontechnical language for nonscientists, disproves this notion. Books such as Albert Einstein and Leopold Infeld’s classic The Evolution of Physics: From Early Concepts to Relativity and Quanta (Simon & Schuster, New York, 1938 and 1966), Brian Greene’s The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory (W. W. Norton & Company, 1999), and Louisa Gilder’s The

Age of Entanglement: When Quantum Physics Was Reborn (Alfred A. Knopf, 2008), illustrate that one can explain physics, including quantum physics, accurately and nontechnically.

CONTENTS
List of Illustrations

Preface
Acknowledgments
1. Introduction: The Tale of the Quantum in the Windowâ
PART 1â•… THE UNIVERSE IS MADE OF QUANTA
2. What Is Quantum Physics About?
3. Particles and Classical Mechanics
4. Fields and Classical Electromagnetism
5. What Is a Quantum?
PART 2â•… HOW QUANTA BEHAVE
6. Perfect Randomness
7. Quantum States and How They Change
8. Superpositions and Macroscopic Quanta
9. An Entangled, Nonlocal Universe
PART 3 GETTING BACK TO THE NORMAL WORLD
10. Schrödinger’s Cat and “Measurement” 191
11. The Environment as Monitor 217
Notes 235
Glossary 261
Index 277